Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.
Catheters are commonly used in medical practice to examine and treat the heart. They may be inserted into the cardiovascular system of the patient through small punctures in the skin, usually in the neck or groin area. Typically, a catheter includes a catheter sheath carrying several electrodes at the tip of the sheath and a control handle for deflecting the tip of the catheter to steer or guide the catheter. The electrodes attached to the catheter sheath can be used to sense electrical signals to identify particular heart conditions or to treat these conditions.
Some catheters carry a multi-electrode loop or lasso structure at the tip of the catheter sheath. One of the advantages of the multi-electrode loop structure is that sensing can be achieved over a larger area. For example, electrical signals can be sensed around an entire pulmonary vein. A catheter, particularly a loop catheter, can sometimes snag on tissue when it is inserted in the vascular system of the patient. In these circumstances, the physician usually tries to free the catheter by pushing or pulling the catheter gently within the vein. Aggressive retraction of the catheter, however, may cause undesirable and dangerous tearing of the tissue or possibly even fracturing of the catheter sheath.